The present invention relates to a developing apparatus which develops an electrostatic image by feeding a toner as a visualizing material in an image forming apparatus represented by, for example, a copying machine of electrophotographic system or a laser beam printer.
Known developing apparatuses which are incorporated in image forming apparatuses using electrophotographic process are of a two-component system which uses a carrier and a toner for a developer, and a one-component system which uses only a toner for a developer. In addition, a proposal has been recently made for a developing apparatus which is of the one-component system and also uses a small amount of magnetic carrier.
Developing apparatuses which are of the one-component system and also use a small amount of magnetic carrier is known from Japanese Patent Application KOKOKU Publication No. 7-40156 and Japanese Patent Application KOKOKU Publication No. 7-43554. These publications disclose an example in which a carrier container area for preventing a toner, which has fallen from a developing sleeve, from being mixed into a toner holding section is positioned below a developing sleeve.
Japanese Patent Appplication KOKAI Publication No. 9-6106 will be cited as an example in which an area for holding a developer is provided under the developing sleeve. According to this publication, a developer is fed by a rotation arm rotated about a rotation center which is positioned lower than the rotation center of the developing sleeve, and a part of a developing housing which holds the developer such that the developer can be fed to the developing sleeve is formed under the developing sleeve.
Each of the developing apparatuses described above has a common feature that the toner is magnetized and a toner layer is formed on the surface of the developing sleeve by a magnetic roller in which N and S poles are provided alternately.
However, in the developing apparatus disclosed in each publication, there is a limitation to the layout of the developing sleeve and the magnetic roller for feeding the toner onto the developing sleeve with predetermined thickness, due to influences from the layout of magnetic poles and the like. Therefore, a problem arises in that all the toner contained in the toner container section of the developing apparatus can not be fed to the developing sleeve.
Hence, in the developing apparatus disclosed in each publication, a toner holding section which is a part of a container area and a developing housing is provided between the magnetic roller and the toner container section.
However, every of the developing apparatuses disclosed in the above described publications has a problem that a large amount of toner remains in the toner holding section in the developing apparatus and a next charge of toner is requested regardless of the remaining toner.